Method of producing a low viscosity, high density fruit juice concentrate



Jan. 30, 1968 R G. SARGEANT 3 366,497

9 METHOD OF PRODUCING A LOW VISCOSITY, HIGH DENSITY vFRUIT JUICECONCENTRATE 7 Filed Feb. 9, 1965 2 Sheets-Sheet 1 ATTORNEY Jan. 30, 1968I R. G, SARGEANT 3,366,497

METHOD OF PRODUCING A LOW VISCOSITY, HIGH DENSITY FRUIT JUICECONCENTRATE Filed Feb. 9, 1965 2 Sheets-Sheet 2 ATTORNEY I United StatesPatent Ofiice 3,366,497 Patented Jan. 30, 1968 3,366,497 METHOD OFPRODUCING A LOW VISCOSITY,

HIGH DENSITY FRUIT JUICE CONCENTRATE Ralph G. Sargeant, Lakeland, Fla.,assignor to Pet Iucorporatetl, St. Louis, Mo., a corporation of DelawareContinuation-impart of application Ser. No. 232,056, Oct. 22,-1962,which is a continuation-impart of application Ser. No. 841,478, Sept.22, 1959, which is a continuatiou-in-part of application Ser. No.482,056, Jan. 17, 1955. This application Feb. 9, 1965, Ser. No. 435,778

2 Claims. (Cl. 99-205) This application is a continuation-in-part of myprior co-pending application Ser. No. 232,056, filed Oct. 22, 1962, andnow abandoned, which application itself was a continuation-in-part of myprior co-pending application Ser. No. 841,478, filed Sept. 22, 1959, nowPatent No. 3,072,490, dated Jan. 8, 1963, which latter application was acontinuation-in-part of my prior application Ser. No. 482,056, filedJan. 17, 1955, and now abandoned.

The invention relates to the preparation of fruit juice concentrateshaving certain desirable characteristics.

As set forth in said prior applications, the present invention mayadvantageously use so-called dielectric heating for evaporating thefruit juices, that is to say, subjecting the juices being treated toelectrical energy in the form of very high frequency oscillations,having a frequency, for example, on the order of to megacycles, more orless.

But the invention, in its broader aspects, is not necessarily limited tothe use of high frequency electrical energy, since the liquid may beevaporated by employing other types of heating means, if desired, such,for example, as low temperature steam evaporators.

The standard commercial practice at present is as described in PatentNo. 2,453,109, MacDowell et al., namely the packaging of a four foldconcentrate having a density of about 42 Brix. This is produced by firstrunning the density up to 55 to 65 Brix and then dilute the concentratewith fresh juice to bring the density down to 42 Brix. The addition offresh juice is necessary to restore the taste and flavor of the productto a degree at which it is acceptable to the public, the original flavorhaving been damaged by the evaporating process.

Commercially, the juice is evaporated by means of steam evaporators,which are similar in construction to water-tube boilers. The verticaltubes are surrounded by hot steam, and the juice flows by gravity downthe tubes, under a partial vacuum. The evaporation of the water dependsupon the conduction of heat by the juice itself. No matter how high thevacuum, or how carefully the temperature is regulated, parts of thejuice are overheated, caramelized, or given a cooked oif flavor. This isdue to the fact that the walls of the steam heated tubes are too hot,and although the juice may fiow along the tubes in the form of a film,the portions of this film in actual contact with the hot walls of thetube become overheated.

As above stated, a density of 42 Brix yields what is cal-led a four foldconcentrate. A density of 72 Brix would yield an eight fold concentrate,which would be highly desirable. Such a high concentrate would have manyadvantages. It would admit of the addition of a larger amount of freshjuice to bring it down to the standard 42 Brix, if desired, for packing.Or it could be packed in the retail cans at 65 or 72 Brix, thus enablingthe purchaser to obtain twice as much reconstituted juice. Or again, itcould be packed in bulk, in large cans or drums, and sold to canners,who might reduce it to 42 Brix and pack it for the retail trade.

This would be especially advantageous for export to foreign countries,since it would result in a big saving in freight costs. Moreover, whilethe 42 Brixconcentrate has to be stored at a temperature close to orbelow zero, the 65 to 72 Brix concentrate will stand storagetemperatures as high as 20 to 30 F. without deterioration.

One of the problems encountered in the concentrated fruit juice industryis caused by the well-known fact that, when a pectin containing juice isheated and then cooled, jellification occurs. This is particularlynoticeable where the juice is concentrated by conventional steamevaporators, in which the juice is subjected to relatively hightemperatures.

In many cases, where an attempt has been made to run the density oforange juice concentrate, for example, up to 65 or 70 Brix with steamevaporators, the concentrate becames very viscous, and tends to gel, andWhen placed in the cans and cooled, was found to be practically solidjelly.

As a result of such jellification, the product, when reconstituted bythe addition of water to produce a juice suitable for drinking, tendedto separate, upon standing, into different strata or layers, instead ofremaining a uniform mixture, and this separating tendency seriouslydetracts from the commercial acceptability of the product.

The degree of jellification and resulting tendency to separate varieswith the temperature to which the juices are subjected duringevaporation, but even with relatively low temperatures these propertiesoccur to a certain extent when using steam evaporators.

For the reasons hereinbefore set forth, it has never been possible, sofar as I am aware, to produce by means of steam evaporators of any kind,a 65 to 72 Brix concentrate satisfactory and acceptable as regards tasteand flavor, and degree of jellification and separation.

It is believed that high frequency oscillations as above mentioned setup electric currents which traverse the liquid materials being treated,and which, in some cases at least, generate heat within these materials.

The rate at which heat is thus generated depends upon the loss factor, afactor which is directly proportional to what is known as the dielectricconstant of the material. Dielectric constants vary from 1 to 8,forfmost materials ordinarily associated with water, but water has adielectric constant of about 80. Thus, the dielectric constant of wateris from ,ten to eighty times greater than that of any other materialwith which water is usually mixed, and therefore water, when subjectedto a high frequency field, heats at a much more rapid rate than anyother such substance or material.

The action of such high frequency oscillations-or field on liquidmixtures is not entirely understood, but it seems probable that in somecases, instead of or in addition to the selective heating effect, theoscillations produce other selective effects on the differentcomponents, possibly related to the above mentioned dielectric constantof each particular material.

The present invention is directed particularly to the problem ofproducing acceptable high density concentrates from fruit juicescontaining substantial amounts of pectin or pectin compounds, such, forexample, as apple juice, grape juice, and citrus fruit juices. Some ofthe citrus fruits, as for example, the popular variety of oranges, knownas pineapple oranges, contain particularly large amounts of pectin (asstated in my prior Patent No. 3,072,490).

The above-mentioned characteristics of jellification and separation areclosely associated with the question of viscosity, so that the higherthe temperature used for evaporation, the higher the viscosity of theproduct. According to one authority, the viscosity of a 72 Brix orangejuice concentrate produced by a steam evaporator at even a relativelylow temperature such as 90 to 120 F. will run at least 20,000centipoises, at 75 F., and even higher. This is due to local overheatingand excessive retention time, resulting in an unacceptably highviscosity.

I have discovered that the problem of jellification and high viscositycan be partially solved by the following method. The whole juice, beforebeing introduced into the evaporator, is first run through a suitablecentrifuge to separate it into two parts. One of these parts is aheavier portion containing most of the water, acids, sugars, etc., andconstituting about 80% of the entire juice. The other part is a lighterportion containing the pectin compounds andeomplexes, as Well as otheringredients such as cellulose fibers, lipids, etc., and constitutingabout 20% of the entire juice. This pectin containing portion is thenstored in a tank or the like, while the watery portion only isevaporated to the desired concentration. By thus first removing thepectin complexes, they are not subjected to the heat of the evaporator.

While I speak of separating the pectin containing portion from the otherportion, it will be understood that such separation is not absolutelycomplete. Thus, the pectin containing portion will contain small amountsof water, sugars, etc., and the watery portion will necessarily containa certain amount of pectincomplexes, cellulose, etc. But'the centrifugeeffects the separation of the major amounts of the several ingredients.

Because of the fact that the watery portion of the juice necessarilycontains a certain amount of pectin, it is highly desirable, whenevaporating this watery portion, to maintain the temperature very low,preferably not over 85 F., the same as when evaporating whole juice, inorder to hold down the viscosity. Moreover, much of the pectin complexesare contained in the cellulose or fibrous material.

After having substantially separated the juice into the two" portionsdescribed, and evaporated the watery portion to the desiredconcentration, several alternate procedures may be followed:

(a) The pectin containing portion, in its natural state, may be at oncerecombined with the concentrated portion to produce the final product.

(b) The pectin containing portion may be heated or flash-pasteurized toinactivate the pectin complexes and any enzymes present before beingrecombined with the concentrated portion.

(c) A small amount of water may be added to the fibrous mass containingthe pectin complexes to thin it, and then the fibrous material may bestrained out and discarded, thus getting rid of the pectin complexeswhich the -fibrous material contained. The liquid passing through thestrainer may be added directly back to the concentrated portion, or itmay be first heat-treated or flashpasteurized.

In any event, the separating out of the major part of the pectincomplexes, concentrating only the remaining, watery portion of thejuice, and thereafter recombining the two portions, results in a productof lower viscosity and less tendency to separate, whatever the method ofevaporating employed.

As above mentioned, I have disclosed in my said prior Patent No.3,072,490 a novel method of evaporating fruit juices by means of highfrequency electrical energy, no part of the juice being raised to atemperature of substantially more than 80 F. At a result, I have beenable to produce an orange juice concentrate of high density and very lowviscosity, possessing a remarkably natural flavor, and having verylittle tendency to jell or to separate.

By employing the high frequency electrical method of evaporating thejuice, disclosed in my said prior patent, and hereinafter described, inconnection with the centrifuge separating method above mentioned, Iobtain even better results, the final product having an extremely lowviscosity, and showing no tendency whatever to jell, or to separate,when reconstituted by the addilion of water. In this manner, I haveproduced concentrated orange juice, for example, having a density of 65Brix, with a viscosity of only 1200 to 1500 centipoises, andconcentrated orange juice having a density of 72 Brix, with a viscosityof not more than 3000 centipoises, at 75 F.

And such high density, low viscosity concentrates, when reconstituted bymixing with water only, without the addition of any fresh juice, providea drink having essentially the same taste and flavor as the juice fromwhich they are prepared.

In carrying out the centrifuge idea in connection with my improved highfrequency electrical evaporator, it will be understood that, instead ofemploying heat or flashpasteurizing to treat the pectin containingportion of the juice, or the liquid remaining after the cellulose fiberhas been strained out, I subject the material to high frequencyelectrical energy. Not only does this result in inactivating the pectincomplexes but seems to have the effect of vaporizing the water molecule,thus stabilizing or inactivating the pectin enzyme.

In order to illustrate the preferred method of carrying out theinvention, independently of the description contained in my said priorapplications, reference is had to the accompanying drawings forming partof this specification, and in which:

FIG. 1 is a schematic view of the essential equipment used in carryingout one form of the invention; 7

FIG. 2 is a sectional plan view on an enlarged scale substantially onthe line 2-2 of FIG. 1;

FIG. 3 is a vertical longitudinal section on an enlarged scale throughmy improved electrode structure;

FIG. 4 is an end elevation of the apparatus shown in FIG. 3, lookingfrom the left;

FIG. 5 is a transverse section substantially on the line 5-5 of FIG. 3,looking in the direction of the arrows;

FIG. 6 is a side elevation of a modified arrangement of electrode andevaporating chamber, parts being broken away; and

FIG. 7 is a horizontal section substantially on the line 77 of FIG. 6,looking in the direction of the arrows.

In the commercial preparation of orange juice, the material, afterhaving been crushed or disintegrated, is usually passed through what isknown as a juice finisher, the purpose of which is to separate the juicefrom the seeds, pulp, etc.

Referring to the drawings in detail, and more especially first to FIG.1, the juice from the finisher is fed into the centrifuge 1 through pipe19. The water-containing portion is delivered from the centrifugethrough pipe 1 to a suitable pump 8, from which it is delivered througha pipe 1 to the conical bottom 10 of an evaporating chamber 10.

From the lower end of the conical bottom 10 extends a pipe 10 to acentrifugal pump 2 which forces the liquid material up through avertical pipe 2 to the top of the evaporating chamber 10 where it isdelivered to a spray head 10 which directs the material into contactwith the vertical walls of the evaporating chamber. The material thenflows down these walls to the conical bottom 10 where it is againrecirculated or recycled by the pump 2.

The preferred construction of the spray head is best shown in FIG. 2. Itconsists of an annular or ring-shaped pipe having a series of nozzles 10projecting outwardly and downwardly from its lower side, so as to spraythe liquid against the walls of the chamber.

Interposed in the pipe 2* is a dielectric heating device or electrodestructure 3 through which the liquids circulate. The details of thepreferred form of this device are shown in FIGS. 3 to 5. It consists ofa horizontally disposed cylindrical casing or shell having a restrictedor tapering end 3 discharging axially of the casing into a pipe 3connected with the spray head Mounted at the other end of thecylindrical structure and extending axially thereof is a centralelectrode in the form of a rod 25, so that an annular space is providedbetween this rod and the cylindrical shell. This central electrode,which is shorter than the cylindrical shell, is supported wholly at oneend, the other end, adjacent the discharge opening of the shell, beingfree. The pipe 2*, which feeds the liquid into the electrode structure,is arranged to deliver the same tangentially into the cylindrical shelladjacent the end at which the electrode rod is mounted, so that theliquid tends to whirl around the annular space as it travels toward thedischarge end of the shell. This whirling or spiral movement of theliquid tends to prevent deposits on the inner surface of the cylindricalshell and keep such Surface clean. Furthermore, it may be desirable insome cases to apply to the surface a protective coating of some suitablematerial such as a silicone, to prevent adhesion.

The inner electrode or rod is supported by a disc 26 of insulatingmaterial, to which it is clamped by means of nuts 31, and the discitself may conveniently be sup ported on the Wall 27 of a suitablehousing having an opening 28. The end of the cylindrical shell or outerelectrode is shown as flanged at 3, and this flange is secured to thewall 27 by means of bolts 29 passing through the flange, the wall 27,and a clamping ring 30. The central electrode is connected with oneterminal of a suitable high-frequency generator by means of a conductor32, secured to the threaded end of the rod 25 by means of a nut 34.Preferably, and as shown, this conductor is in the form of a coppertube, having its end flattened and perforated as at 33, for attachmentto the electrode rod, and cooled by water circulating therethrough bymeans of hose connections 35. Owing to the skin effect of high frequencycurrents, the electrical energy is carried mostly on the surface of theelectrode rod 25, and it is advantageous to have this rod, which may beof stainless steel, plated with a good conducting non-corrosive metalsuch as silver.

In use, the elect-rode structure is connected with the two sides of ahigh-frequency generator 36, one side being connected through a wellinsulated lead 36 with the central rod 25, and the other side connectedby lead 36 with the electrode shell or casing, which is grounded.Preferably, and as usual in the art, such connection is made by means ofa coaxial cable.

The pectin-carrying components of the juice are dis charged from thecentrifuge 1 through the pipe to a suitably refrigerated storage tank,where they are held in storage until the water-carrying component whichis being recirculated through the evaporating chamber as above describedhas reached the desired concentration. Samples of the product can bewithdrawn from time to time through spigot 18 for testing, to determinewhen the desired concentration has been reached. This concentratedcomponent is then withdrawn through valve 7 and thereafter recombinedwith the stored pectin-carrying component to produce the desired finalproduct. As above explained, this pectin-carrying component may berecombined with the concentrated component either in its natural state,or after having been treated in any one of several ways to reduce thepectin content or inactivate the pectin-enzymes, so as to reduce thetendency of the product to jellify.

By thu separating the juice into two components and evaporating only oneof these components, a very substantial saving in power results, and thetime cycle is also greatly reduced. Furthermore, the pectin-carryingcomponents of the juice are not exposed to the heat of evaporation andconsequently the final product does not tend to jell when cooled.

From the top of the evaporating chamber 10 extends a pipe 4 to acondenser 4 of any suitable type shown as a shell and tube condenserhaving tube sheets or bulk 6 heads 4' adjacent each end, between whichextend tubes 4".

A pipe 4 extends from the bottom of the condenser 4 to a steam-operatedair ejector 5, supplied with steam through a pipe 12. This ejector drawsthe vapors from the evaporating chamber down through the tubes of thecondenser 4, and the steam and vapors are delivered from the ejector 5through a pipe 14 into an intercondenser 17. A second air ejector 5'draws the uncondensed steam and vapors from the condenser 17 anddischarges through pipe 14' to atmosphere. To eliminate the costlyconstruction required with a barometric condenser such as is commonlyused for this purpose, I employ a surface-type condenser, containing acoil 17. Water is fed to one end of this coil by a pipe 13, and from theother end extends a pipe 13' to a jacket 9 which surrounds theevaporating chamber 10. Thus, the water which is heated in the coil 17by the steam and vapors from the air ejector 5 is utilized to transferthis heat to the walls of the evaporating chamber 10. As the liquidmaterial flows down inside of these walls, it is maintained at arelatively warm temperature by the water jacket 9 and prevented fromcooling off substantially as it otherwise would do. A pipe 23,controlled by a valve 24, is connected with pipe 13, and through thispipe 23 cold water may be admitted to regulate the temperature of thejacket 9 as desired.

By way of example, it may be stated that by means of the air ejectorabove described, a vacuum is maintained on the evaporating chamber to anextent of at least 29 /2 inches, so that the water contained in theliquid mixture being treated evaporates at about 70 F., and thetemperature of the water jacket 9 is such that the temperature of theliquid being evaporated as it flows down the walls of the chamber 10does not fall substantially below 75 F. By virtue of utilizing the heatfrom the condenser 17 by means of this water jacket 9, the amount ofpower required to be delivered to the electrode structure 3 is greatlyreduced, thus eflecting a substantial economy. In practice, the level ofthe liquid being treated in the evaporating chamber is maintainedapproximately at the upper end of the conical bottom 10* thus permittingthe liquid to flow down the entire length of the water-jacketed walls.In order to observe the level of the liquid in the evaporating chamber,a sight glass 22 is preferably provided adjacent the bottom thereof.

A suitable refrigeration medium such as Freon gas is supplied to thecondenser 4 by pipes 11, from a suitable compressor, in a well-knownmanner, this apparatus being so designed as to maintain the condenser 4at a temperature of approximately 50 F. Thus the vapors coming offthrough pipe 4 are mostly condensed, and the condensate flows out fromthe bottom of the condenser through pipe 20 to a pump 6. A pipe 21 fromthe bottom of condenser 17 delivers additional condensate into the pipe20.

Water fed into the condenser coil 17* may be derived from any suitablesource, but a further economy may be achieved-by utilizing water fromthe condenser of the compressor supplying the refrigerating medium tocondenser 4 as above described. Thus, water may be caused to flowcontinuously first through the compressor condenser and then through thecoil 17* to the jacket 9, from which it escapes through pipe 16. Thiswater absorbs heat from the compressor condenser and is somewhat Warmwhen it enters the coil 17*. It is then further heated by the steam fromejector 5 before passing on to the water jacket.

While I have shown and described a centrifuge for separating the freshjuice into two components, only one of which is subjected toevaporation, it will of course be understood that the separating stepmay be omitted if desired and the whole juice concentrated by means ofmy improved evaporator system. This has been done successfully, with theresults described in detail hereinafter.

Where the whole juice is evaporated, my improved method has a specialadvantage in connection with the pectin present in the juice. Byemploying high frequency electrical energy, and operating at a very lowtemperature and under a high vacuum, no portion of the juice is heatedto a point high enough to cause the pectin, when the juice is cooled, totend to jell. This avoidance of jellification may be due, as abovestated, to the fact that the temperature of all portions of the juice ismaintained below the critical temperature at which the pectin is causedto jell, or it may be that the high frequency electrical energy to whichthe juice is subjected has an effect on the pectin, or may break down orchange the character of the enzymes. present. In any event, the fact isthat juice evaporated and concentrated in accordance with my improvedmethod shows no tendency to jellify when cooled, and, when reconstitutedby mixing with water, shows no tendency to separate. This in itself is anovel and important achievement.

Refer-ring again to FIG. 1, the pipe 2 is slIghtly larger than therestricted outlet 3- discharging the juice from the electrode structure,so that the pump 2 tends to generate a substantial pressure within theelectrode structure. Thus, the high frequency electrical energy isapplied to the juice while it is under pressure.

Furthermore, the sum total of the areas of the spray nozzles ispreferably somewhat greater than the crosssectional area of therestricted discharge 3 with the result that the pressure in the sprayhead 10* is somewhat less than in the electrode structure.

The high frequency generator 36 which I employ is of the well known typeembodying one or more oscillating thermionic tubes. The exact frequencyis not critical, but should be what is known as radio frequency. Forexample, a frequency of 60 cycles per second, such as ordinary housecurrent, would not be high enough to produce the desired results.Furthermore, with such a low frequency current electrolysis is likely tooccur at the inner electrode. It is thought that a frequency of anywherewithin the range of 1 to 25 or more megacycles will operatesatisfactorily. In practice, I have usually employed a frequency on theorder of to megacycles. In any event, the important thing is that theelectrode structure be so proportioned as to be electrically resonant tothe frequency employed.

The juice passing through the electrode structure 3 is usually heated.The difference in temperature of the juice entering and leaving theelectrode structure is referred to as the temperature differential. Theapparatus has been operated with a temperature differential as high as40 F., and again it has been operated with a very small temperaturedifferential of not more than one or two degrees F. A temperaturedifferential of 5 to 10 F. gives satisfactory results.

The temperature differential depends, of course, on the rate of flow ofthe juice through the electrode structure and on the amount ofelectrical energy supplied by the generator. Apparently the lower thetemperature differential, the better the product obtained.

If, as has been done successfully, the temperature differential is heldat near zero, such, for example, as 1 or 2, then there is practically nosensible heating of the juice as it passes through the electrodestructure. The high frequency energy may have some effect other thanheating. For example, the high frequency electrical energy may operateto produce a separation of the water particles or molecules from theother components. It is not known with certainty just what effect thehigh frequency energy has on the liquid mixture, but the fact is thatthe application of such high frequency energy to the liquid mixtureproduces the results described herein.

A vacuum of at least 29" to 29 /2" of mercury is maintained in theevaporating chamber 10 and the water in the jacket 9 is regulated so asto keep the temperature of this chamber at around 75 F. When the liquidmixture is sprayed into this chamber through the spray nozzles 10 thewater present immediately flashes into steam or vapor which is drawn offthrough the conduit 4. As the water vaporizes, it absorbs a large amountof heat, namely, the so-called latent heat of vaporization.

It will be understood that the electrode structure, when operating, isnot hot to the touch, and that, when the rate of flow is such as tomaintain only a small temperature differential between the inlet anddischarge ends, it is difficult to detect any sensible heating. In hotweather, the juice is preferably first refrigerat-er or cooled, so thatit comes into the electrode structure at a temperature no higher than 60to 65 F. If then it is heated 5 to 10 F. by the electrical energy, it isdischarged into the vacuum chamber at 65 to 75 F., at which temperature,under the high vacuum employed, the water flashes into vapor, as abovementioned. This temperature of not over 85 F. is, of course, not highenough to sterilize the product. Thus, the concentrate, as alreadymentioned, has to be stored under refrigeration.

It will be particularly noted that at no point in the cycle does theliquid come in contact with any surface hotter than 75 to 85 F. This isin sharp contrast to the temperature of 130 to 140 F. encountered in theconventional steam evaporators.

By way of example, but in no sense as a limitation, the followingfigures may be given. With an electrode structure having an outsidediameter of 3" to 4" and a length of 18" to 20", an inner electrodeabout A" in diameter and 12" or 14" long is employed. The pump 2generates a hydraulic pressure of as high as 60 lbs. per square inch inthe electrode structure and, as above described, this is reduced toabout 25 lbs. per square inch at the spray head. The rate of flowthrough the electrode structure may be on the order of 30 gallons perminute, but of course this may be varied by controlling the speed of thepump. The amount of electrical energy supplied to the electrodestructure is on the order of 9 kilowatts.

With equipment such as described in the foregoing example, it ispossible to produce an orange juice concentrate having a density of ashigh as Brix, without any caramelization or off flavor. At the sametime, owing to the fact that the temperature of the juice at all pointsis maintained very low, the viscosity is exceptionally low.

Tests have been run, among others, with the whole juice of the pineapplevariety of orange, which variety, as already stated, is known to containa large amount of pectin. At a density of 65 Brix, for example, theviscosity of this concentrate at 75 F. was on the order of 1200 to 1500centipoises, and at a density of 72 Brix did not exceed about 3000centipoises. This compares with a viscosity of around 15,000 to 20,000centipoises for the same concentrate brought to the same density by thethermal conduction method in the conventional steam evaporator. Thus,the viscosity of the high density concentrate prepared by my improvedmethod is only a fraction of that of concentrates of the same densityprepared by convention-a1 methods. More specifically, it is less thanhalf. So far as I am aware, I am the first to produce an orange juiceconcentrate having so high a density combined with such a low viscosity.

This low viscosity is due in part at least to the fact that the liquidis heated with absolute uniformity as it passes through the electrodestructure when employing a temperature differential high enough tosubstantially heat the liquid.

When thus regarding my improved electrode structure as a heating device,it is apparent that the electrical energy is applied across ortransversely of the mass of liquid. If the high frequency electricalenergy may be regarded as a current, this current flows radially throughthe annular mass of liquid, thus uniformly heating all portions thereof.In other words, the same heating effect is applied at all pointsthroughout the mass.

It seems to be a fact that, as set forth herein, the water present inthe liquid mixture heats first, and faster than the other components.This, as above explained, is due to the very high dielectric constant ofwater. So, when I say that all portions of the liquid mixture areuniformly heated, I mean that there is no zone, point, stratum or layerof the mass that is subjected to any greater heating eflect than anyother zone, point, stratum or layer, and use of the expression uniformlyheated is not intended to exclude the possibility that, because of theircharacter, some components distributed through the mass may be heatedfaster or more strongly than others.

This idea of uniformly heating all portions of the liquid is in sharpcontrast to the conventional commercial systems in which steamevaporators are employed. As above mentioned, in these commercialplants, in which the liquid being treated flows through steam heatedtubes and is heated by conduction, the portions or layers of the liquidin direct contact with the hot walls of the tubes are heated to a muchhigher temperature than the other portions. And this is true, eventhough the liquid flows along the tubes in the form of a relatively thinfiim. It is for this reason that, in the case of citrus juice, it isimpossible to avoid a certain amount of caramelization, and relativelyhigh viscosity, as the density increases.

Under some circumstances, I have found it desirable to concentrate thecitrus juice first by means of a conventional evaporator using thethermal conduction method until a density of 50 to 55 Brix is reached,and then introduce this partially concentrated product into my improvedhigh frequency electrical apparatus herein described, where the densityis carried up to 72 to 80 Brix, Without producing any caramelizat-ion oroff flavor.

By employing the centrifuge step and carrying out the entire operationfrom start to finish by means of my improved high frequency electricalapparatus 'as herein described, I am able to reduce the viscosity of thefinal product still further. For example, I can produce a concentrate ofa density of 72 Brix having an unprecedentedly low viscosity of only2500 to 2700 centipoises, at 75 F.

What I claim is:

1. The method of producing a low viscosity concentrate from citrus juicecontaining a substantial amount of pectin; said concentrate having adensity of at least 72 Brix, and capable of being reconstituted bymixing with water alone, without the addition of fresh juice, to providea drink having a flavor essentially the same as that of the juice fromwhich the product is prepared, comprising first centrifuging the wholejuice to substantially separate the pectin-containing portion from thewater-containing portion, storing the pectin-containing portion in asuitable receptacle, causing the water-containing portion only to flowin the form of a solid, confined stream under substantial hydraulicpressure through a high frequency dielectric heating device directlyinto a partial vacuum, regulating the amount of electrical power and therate of flow of the juice portion in such manner that the temperaturedifferential between the liquid entering and leaving said heating deviceis maintained within a range of 2 to 40 F., controlling the temperatureand pressure of said partial vacuum so that the water present in thejuice portion entering the same flashes into vapor, continuing suchevaporation until the juice portion reaches a concentration having adensity greater than that of the final product, and thereafterrecombining said concentrated juice portion with said pectin-containingportion to produce the desired low viscosity product.

2. In the preparation of high density, low viscosity concentrate-s fromfruit juices containing substantial amounts of pectin, the method ofeliminating any tendency of the concentrated product to jell whencooled, and to separate when reconstituted by mixing with water, whichcomprises first centrifuging the Whole juice to substantially divide itinto two portions, namely a portion containing most of the water, sugarsand acids, and a portion contain-ing the major part of the pectin,cellulose and lipids, storing the pectin-containing portion in asuitable receptacle, causing the water-containing portion alone to flowin a confined stream along a closed path under substantial hydraulicpressure, applying to such portion of the juice while so flowing highfrequency electrical energy, discharging the stream at the end of suchclosed path into a partial vacuum, controlling the temperature andpressure of said partial vacuum so that the Water present flashes intovapor, leaving a concentrated residue having a density greater than thatof the final product, and finally recombining this concentrated residuewith said pectin-containing portion to produce the desire-d product.

References Cited UNITED STATES PATENTS 2,602,134 7/1952 Nelson 99208 X2,724,652 11/ 19-55 Brent et val. 22-205 3,072,490 1/ 1963 Sargeant99-205 HYMAN LORD, Primary Examiner.

A. LOUIS MONACELL, Examiner.

R. S. AULL, Assistant Examiner.

1. THE METHOD OF PRODUCING A LOW VISCOSITY CONCENTRATE FROM CITRUS JUICECONTAINING A SUBSTANTIAL AMOUNT OF PECTIN; SAID CONCENTRATE HAVING ADENSITY OF AT LEAST 72* BRIX, AND CAPABLE OF BEING RECONSTITUTED BYMIXING WITH WATER ALONE, WITHOUT THE ADDITION OF FRESH JUICE, TO PROVIDEA DRINK HAVING A FLAVOR ESSENTIALLY THE SAME AS THAT OF THE JUICE FROMWHICH THE PRODUCT IS PREPARED, COMPRISING FIRST CENTRIFUGING THE WHOLEJUICE TO SUBSTANTIALLY SEPARATE THE PECTIN-CONTAINING PORTION FROM THEWATER-CONTAINING PORTION, STORING THE PECTIN-CONTAINING PORITION ONLY TOFLOW IN THE FORM OF A SOLID, CONFINED STREAM UNDER SUBSTANTIAL HYDRAULICPRESSURE THROUGH A HIGH FREQUENCY DIELECTRIC HEATING DEVICE DIRECTLYINTO A PARTIAL VACUUM, REGULATING THE AMOUNT OF ELECTRICAL POWER AND THERATE OF FLOW OF THE JUICE PORTION IN SUCH MANNER THAT THE TEMPERATUREDIFFERENTIAL BETWEEN THE LIQUID ENTERING AND LEAVING SAID HEATING DEVICEIS MAINTAINED WITHIN A RANGE OF 2* TO 40*F., CONTROLLING THE TEMPERATUREAND PRESSURE OF SAID PARTIAL VACUUM SO THAT THE WATER PRESENT IN THEJUICE PORTION ENTERING THE SAME FLASHES INTO VAPOR, CONTINUING SUCHEVAPORATION UNTIL THE JUICE PORTION REACHES A CONCENTRATION HAVING ADENSITY GREATER THAN THAT OF THE FINAL PRODUCT, AND THEREAFTERRECOMBINING SAID CONCENTRATED JUICE PORTION WITH SAID PECTIN-CONTAININGFPORTION TO PRODUCE THE DESIRED LOW VISCOSITY PRODUCT.